AGR 3102AGR 3102Principles of Weed SciencePrinciples of Weed Science

Unit 5:Unit 5:Methods of Weed ControlMethods of Weed ControlMechanical and CulturalMechanical and Cultural

Muhammad Saiful Ahmad HamdaniMuhammad Saiful Ahmad Hamdani

Methods of Weed ControlMethods of Weed Control

• Objective: to injure/kill weed plants physically and use physical barrier to impede weed growth.

• Consists of:

1. Hand pulling and hoeing: can be expensive (labour cost). Good for garden & small areas.

2. Tillage: burial, exposing weed seeds, pull-out de-rooting.

3. Mowing and slashing: more effective for tall-growing weeds; repetition may prevent seed production. More effective on broadleaf weeds than on grasses.

Tine harrowing-remove weed seedlings

PloughingPloughing

Slashing

Hand-hoeingHand-hoeing

4. Weed seed destroyer – in Australia.

• Designed to destroy weed seeds during harvest and thereby reducing the potential for weed growth.

• Towed behind a harvester. • Used in grain crop areas.

5. Burning and heat:

- Steam sterilization of potting media for nursery operations; kills weed propagules (veg. parts), insects, pathogens.

- Kill most emerged weeds and seeds.

- However, lose benefit of allelopathy from straw; also eliminates potential for organic matter.

• Windrow burning

in Australia

• Rice straw burning

in Malaysia

6. Mulching

• Reduced/blocked light and air penetration into soil: impede/prevent weed seed germination and growth.

• Materials used: hay, woodchips, rocks, sawdust, plastic mulch used in horticultural crops.

Disadvantages of Mechanical ControlDisadvantages of Mechanical Control

Not completely eradicate weeds.

Not a long lasting control methods.

High cost is needed (labor, machineries).

High time and energy consuming.

Need high efficacy esp. for control method using hoe and machineries. If not careful, might also destroy crops.

Methods of Weed ControlMethods of Weed Control

• Objective: provides conditions more favourable for

crop growth, less favourable for weeds. Involves agronomic practices and crop management.

• Consists of:

1) Grow Healthy & Competitive Crops:

Select competitive & resistant varietiesSelect competitive & resistant varieties

Provide optimal growing conditions for Provide optimal growing conditions for

crops – suitable soil type, pHcrops – suitable soil type, pH

Irrigate and fertilize crop, not weedsIrrigate and fertilize crop, not weeds

Early/delay sowing date – e.g. in rice farmingEarly/delay sowing date – e.g. in rice farming

Intercropping – using empty space between crop rowsIntercropping – using empty space between crop rows

Crop rotation: Crop rotation can disrupt weed life cycles. Crop rotation: diversity in herbicides use.

High seeding rate - higher seeding rates increase planting density and planting uniformity: no space for weeds.

HOWEVER!!!HOWEVER!!!

- not to be so high that yields are reduced (intraspecific competition, high humidity, lodging, disease potential)

2) Cover Crops:

• Used to compete with the weeds infesting an area.

• Prevent weed emergence and/or reduces growth of weeds.

• Can exclude light, provide a physical barrier to weed emergence, modify soil temperature and moisture, increase N2 fixation, become fertilizer to crops.

• Allelopathic chemicals from the cover crop residue may also inhibit germination/growth of weeds.

3) Water Management:

• Flooding used in rice production for weed control.

• Many weeds are not tolerant to anaerobic conditions: death. Rice can survive flooding. Less suitable for aquatic weeds.

• Water deprivation can be a weed control method in orchard or plantation.

Disadvantages of Cultural ControlDisadvantages of Cultural Control

Some methods consume large amount of natural resource (e.g. water).

Weeds are even more aggressive than the latest variety.

Crop rotation, not applicable in plantation and perennials.

Cover crops is not suitable for some crops.

Need high efficacy esp. for control method using precise irrigation and fertilizers, not practical in rice field.